Since the Industrial Revolution, the planet has warmed by roughly one degree.

2013 marked the 37th consecutive year of above-average temperatures. Fully 4 billion people alive today have never experienced a year that was cooler than last century's average.

If we continue with business as usual, burning ever more oil, coal, and natural gas, the global average temperature is projected to rise some 11 degrees Fahrenheit (6 degrees Celsius) by the end of this century.

In addition to more widespread drought and more numerous wildfires, climate change brings more extreme heat waves.

In the last decade, daily record high temperatures outnumbered record lows in the United States two to one, and that ratio is increasing.

Crop ecologists have a rule of thumb that each 1-degree-Celsius rise in temperature above the norm during the growing season lowers wheat, rice, and corn yields by 10 percent. Field tests show that this may be conservative.

This century, as waters warm and ice continues to melt, seas are projected to rise some 2 meters (6 feet), inundating coastal cities worldwide, such as New York, London, and Cairo, and agricultural hotspots, like rice-growing river deltas.